The contract will provide a virologic quality control program which is critical for the scientific integrity of the collaborative extramural clinical and epidemiologic studies supported by the NIAID AIDS Program. The contractor shall be responsible for the preparation of standard virus stocks, antigens, and probes, for distributing them to the research sites, for routine quality assurance checks on virologic assays conducted at the research sites, and for supporting the development of new assays of viral infection by field testing their usefulness in multicenter investigation.